The hydraulic module comprises a plate heat exchanger, an outlet valve, and an inlet valve, serving as a critical component for controlling the water circuit system in gas-fired wall-mounted boilers. By connecting to the primary heat exchanger, cold water inlet, hot water outlet, and external radiator, it switches between the heating circulation loop and the domestic hot water circulation loop according to user demand. The hydraulic module is equipped with monitoring ports for system pressure, flow rate, temperature, and other parameters.